CREATE PROCEDURE selling     @ID varchar(40),@yaopin_id varchar(40),
 @price smallmoney ,@zhekou real, @sellprice smallmoney,@unit varchar(10), @num smallint
 AS
DECLARE @cost smallmoney
DECLARE @N smallint
select @cost=cost from yaopin_cost where id=@yaopin_id
select @N=switch FROM yaopin_unit WHERE id=@yaopin_id  AND unit=@unit
insert into sell_list values (@id,@yaopin_id,@cost*@N,@price,@zhekou,@sellprice,@unit,@num*@N)
update yaopin_num set num=num-@num*@N where id=@yaopin_id
GO